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Summary This paper provides relevant information for veterinarians responsible for treatment of endurance horses, including a retrospective study of fractures in endurance horses presenting to one referral hospital and to treatment clinics at 3 different race venues. Treatment and case outcome were also noted. The information presented provides clinicians working with high level endurance horses increased awareness of common sites of fractures, of prefracture stress related bone injury within this population of athletes and guidelines in order to manage them more effectively. The most common fractures involve the metacarpo‐(tarso‐)phalangeal joint. Most distal limb fractures can be diagnosed radiographically, but magnetic resonance imaging or scintigraphy may be required in some cases.

Summary Reasons for performing study: Sclerosis of the third carpal bone is a common radiographic finding in both lame and sound racehorses, but there are no guidelines correlating degree of sclerosis and incidence of lameness. Objectives: To develop a protocol for describing subchondral bone sclerosis in C3 on dorsoproximal‐dorsodistal oblique (DPr‐DDiO) radiographs of the carpus and to correlate these changes with exercise history and carpal lameness. Methods: One hundred and six Standardbreds entering their first year of training (exercise group) and 7 age‐matched Standardbreds at pasture (controls) were examined at approximately 3 month intervals over 12‐18 months. Examinations consisted of lameness evaluation and carpal radiographs (DPr‐DDiO and flexed lateromedial projections). A grading system (very mild, mild, moderate and severe) for C3 sclerosis seen on the DPr‐DDiO radiograph was developed that utilised a combination of the criteria of trabecular thickening (trabecular score; TS) and total percent area of the C3 radial facet affected (TAA). Results: Exercise group horses showed significant increase in TS and TAA throughout training compared to control horses. Middle carpal joint lameness developed in 32/106 (30%) exercise group horses and none of the control horses. Incidence of middle carpal joint (MCJ) lameness was lower in horses with mild (2/30, 6.7%) than moderate (10/32, 31.2%) and severe (20/44, 45.4%) sclerosis throughout training. Conclusions: Horses with higher grades of sclerosis, as defined by this novel grading system, were more likely to develop MCJ lameness at some point of training. The proposed grading system gave a quantitative assessment of radiographic sclerosis that could then be used to correlate increasing severity of sclerosis with increasing incidences of lameness. Potential relevance: These results serve as a basis for further investigation into determining the degree of C3 sclerosis at which pathological changes and lameness can be expected.

Transection of the accessory ligament of the SDF muscle may predispose horses to SL desmitis postoperatively.

Summary Reasons for performing study: Lameness related to the middle carpal joint (MCJ) occurs in up to 30% of young Standardbred horses in race training and the incidence increase with radiographic severity of third carpal bone (C3) sclerosis on DPr‐DDIO (skyline) view of the carpus. Factors predisposing horses to carpal injury have not been well investigated. Objectives: To determine the importance of MCJ lameness as a cause of wastage in young Standardbred racehorses, stage of training at which it occurs and predisposing factors, and to describe clinical findings and diagnosis. Methods: Standardbred horses (n = 114) entering their first year of race training were examined at approximately 3‐month intervals over 12–18 months. For 87 of the horses, a training diary was available and these horses were trained at 3 different stables, each using a different exercise regime. At each examination, forelimb conformation, MCJ effusion, MCJ lameness and radiographic findings were graded, and training history and reasons for lost training days recorded. Nuclear scintigraphy and exploratory arthroscopy were performed on a limited selection of horses. Results for horses that developed MCJ lameness during the study period were compared statistically with results for horses that did not. Results: Carpal lameness occurred in 28% of horses and was present in 56% with forelimb lameness. In most cases lameness was mild, bilateral and with little or no MCJ effusion and was attributed to subchondral bone pain associated with radiographic evidence of C3 sclerosis. Carpal lameness was the most common reason for >1 month's rest during the study period. It occurred at any stage of training but, in most cases, some speed training had begun. Of the variables studied, poor forelimb conformation and more intense speed training were predisposing factors. Conclusions and potential relevance: The information gained should assist in making recommendations regarding training young Standardbreds to reduce the incidence of MCJ lameness. However, further investigations to determine the optimal training regime are warranted.